Sensitizing dyes containing a 6-beta-cyanoethoxy-benzothiazole dye nucleus



3,062,815 Patented Nov. 6, 1962 United tates The reaction which as carried out at elevated tempera- 3062815 tures, preferably exceeding those of the boiling point of the solvent-diluent, or of the acrylonitrile when using an Curt Roth, mnghamton, Lester Horwitz, Bronx and excess thereof in place of the solvent-diluent, is illustrated Harold A. Levine, Binghamton, N.Y., assignors to Geu- 5 by the fOhOWlhg formulae: eral Aniline & Film Corporation, New York, N.Y., a

corporation of lgelaware 31 1959 S N 863 087 110- N Drawing. iled Dec. er. 0. ()H CH CH-ON Claims. (Cl. Eco-i405 3+ F This invention relates to sensitizing dyes derived from 2-methyl-6-B-cyanoethoxy benzothiazole and the silver S halide emulsions sensitized with such dyes. NO OH OH O Benzothiazole radicals which are substituted in the 6- position by a hydroxy, acetoxy or carboxyethoxy group N have already been used in the preparation of certain cyanine dyes. However, no dyes have been described so Wherelh R has the Yahles gweh abovefar which contain benzothiazole nuclei in which a cyano- The e- Obtalhed e ethohy'subshmted ethyl group is attached to the 6-position of the benzobehzhthlazele base may be readlly luatemlzed by Q thiazole by means of an ether linkage vent1onal methods to produce the desired cyclammonium We have now found that extremely valuable sensitizing quaternary salts for the eyahlhe dye syhthesls- For dyes can be prepared from benzothiazoles which contain a f The methiodide and theethiedide are h h by methyl group in the 2-position, a hydrogen atom or methyl heahhg the base Wlth methyl lodlde or ethyl re; group in the 5 position and a cyanoethoxy group in the spectively, under pressure in a sealed container for sev- 6-position. These bases which are readily quaternized eral hours at 96-1OO e quaternary Salts Obtained by conventional methods can be reacted with cyclalm are characterized by the following general formula: monium quaternary salts containing a reactive group in S the u-carbon to produce, inter alia, monoand poly- NC-CHzCHz-O methine cyanine dyes which are valuable sensitizers for 0-0113 silver halide emulsions. R

Among the objects of our invention are sensitizing N dyes containing a 6-[3-cyanoethoxy benzothiazole nucleus and silver halide emulsions sensitized with said dyes.

The new bases which form the starting materials in such dyes are 2-rnethyl-6-(B-cyanoethoxy) -benzothiazoles having the following general structure:

wherein R has the value given above; R is alkyl such as methyl, ethyl, propyl, fi-hydroxyethyl, 'y-hydroxypropyl, allyl and the like; carboxyalkyl, such as carboxymethyl, carboxyethyl, and the like; aralkyl, e.g., benzyl, phen ethyl and the like; and X is an anion such as chloride, rbromide, iodide, ethylsulfate, perchlorate, p-toluenesul- 043E: 40 fonate, and the like. The above quaternary ammonium salts may be con- N verted into sensitizing dyes characterized by the following wherein R is a hydrogen atom or a methyl group. general formulae:

NC-CHaCH2-O R1 I Y- These compounds are prepared by reacting Z-methylwherein R and R have the values given above; m, n and 6-hydroxybenzothiazole or 2,5-dirnethyl-6-hydroxybenzop represent a positive integer of from 1 to 2; R and R thiazole with a molar excess of acrylonitrile in the presare either hydrogen or a lower alkyl group, e.g., methyl, ence of a suitable basic catalyzing agent such as a terethyl, propyl, and the like; R being only hydrogen when tiary amine, e.g., triethylamine, trimethylamine, tri-nn and p equal 1; R represents an alkyl group such as butylamine, tri-n-proplyarnine; a quaternary ammonium methyl, ethyl, propyl, butyl, amyl; a hydroxyalkyl group hydroxide, e.g., benzyltrimethylamrnonium hydroxide, such as hydroxymethyl, hydroxyethyl, hydroxypropyl cetylethyldimethylammonium hydroxide or cetyltriand the like; carboxyalkyl such as carboxymethyl, carmethylammonium hydroxide. The desired dilution can boxyethyl, carboxypropyl and the like; aralkyl, e.g., be obtained by the use of an excess of acrylonitrile or by y Phenethyl and the likfi; Y presents an anionic the selection of a suitable solvent such as benzene, toluene radical, 1, 4, 4 3 4 2 5,

and the like. S03C5H4OH3 and the like; and Z represents the hetero atoms necessary to complete a or 6-membered nitrogenous heterocyclic system of the type used in cyanine dyes, such as pyridine, lepidine, quinoline, indoline, oxazole, thiazoline, thiazole, selenazole, selenazoline, oxazoline, benzothiazole, benzoselenazole, benzoxazole, naphthothiazole, and the like.

These sensitizing dyes are prepared by heating the above G-(fl-cyanoethoxy)-benzothiazolium salts in the presence of an acid binding agent such as pyridine, trimethylamine, triethylamine and the like with a cyclammonium quaternary salt having a reactive grouping on the carbon atom in the 2-position of the heterocyclic ring, for instance, a halogen atom, e.g., chlorine, bromine, or the like; an alkylmercapto group, e.g., methylmercapto, ethylmercapto, and the like; an alkylmercaptovinyl group, e.g., ,B-methylmercaptovinyl, ,B-ethylmercaptovinyl and the like; a fl-alkylmercapto-B-alkylvinyl group, e.g., fi-methylmercapto-fl-methylvinyl, fl-ethylmercapto-B-ethylvinyl and the like; [i-acetanilidovinyl, 4-acetanilido-1,3- butadienyl, and 6-acetanilido-1,3,5-hexatrienyl.

As examples of suitable cyclammonium quaternary cyanine dye salt intermediates having a reactive group in the 2-position to the nitrogen atom thereof so as to form a monomethine dye, the following may be mentioned:

Z-methylmercapto-6-methylquinoline ethiodide 2-methylmercapto-6-methoxyquinoline ethiodide 2-methylmercaptopyridine ethiodide 2-methylmercaptothiazoline ethiodide 2-phenylmercaptothiazoline ethiodide, and the like In preparing trimethine cyanine dye salts, the following cyclammonium quaternary dye salt intermediates having a reactive group in the fi-position of the side chain in the 2-position of the nitrogen atom thereof may be employed:

Z-(fi-acetanilidovinyl)-thiazoline ethiodide Z-(B-acetanilidovinyl)-benzothiazole ethiodide 2-(p-acetanilidovinyl)-benzoxazole ethiodide Z-(fi-ethyl ,B ethylmercaptoviuyl) 5 methoxybenzoselenazole ethiodide 2 (/3 methylmercapto )3 methylvinyl) benzothiazole ethiodide 2 (,3 mcthylmercapto B propylvinyl) benzothiazole ethiodide In preparing pentamethine and heptamethine cyanine dyes, the following cyclammonium quaternary salts having a reactive group in the deltaand omega-positions of the side chain in the 2-position of the nitrogen atom thereof may be employed:

2-(4-acetanilido-1,3-butadienyl)pyridine ethiodide 2-(4-acetanilido-1,3-butadienyl)benzoxazole ethiodide 2-(4-anilino-3-methyl-l,3-butadienyl)pyridine ethiodide 2-(4-anilino-3-methyl-1,3-butadienyl) 18 naphthoxazole ethiodide 2 (4 anilino-3-ethyl-1,3-butadienyl-a-naphthothiazole ethiodide 2-(6-anilino-1,3,5-hexatrienyl)thiazoline ethiodide 2-(6-anilino-1,3,5-hexatrienyl) a naphthothiazole ethiodide 2 (6 anilino-l,3,5-hexatrienyl)-fi-naphthothiazole ethiodide 2 (6-anilino-1,3,5-hexatrienyl) -a-naphthoselenazo1e ethiodide 2-(6-anilino 1,3,5 hexatrienyl) ,8 naphthoselenazole ethiodide 2-(6-anilino 4 methyl 1,3,5 hexatrienyDthiazoline ethiodide 2-(6-anilino-4-methyl 1,3,5 hexatrienyl)benzothiazole ethiodide 2-(6-anilino 4 butyl 1,3,5 hexatrienyl)benzothiazole ethiodide We have found that our new dyes are especially useful for extending the spectral sensitivity of the customarily employed silver chloride, silver chlorobromide, silver bromide, silver bromoiodide and silver chlorobromoiodide developing out emulsions. The dyes are equally effective in gelatin emulsions and in those emulsions in which a synthetic colloidal carrier such as modified polyvinyl alcohol is employed.

To prepare emulsions sensitized with one or more of our new dyes, it is only necessary to distribute homogeneously the dye or dyes in the photographic emulsions. The methods of incorporating dyes in emulsions are simple and are well known to those skilled in the art. In practice, it is convenient to add the dyes to the emulsions in the form of a solution in an appropriate solvent. Methanol has proved satisfactory for our new dyes; dimethylformamide or a mixture of acetone and freshly distilled pyridine may also be employed as a solvent. The dyes are advantageously incorporated in the finished, washed emulsions and should be uniformly dis tributed throughout the emulsions.

The concentrations of the dyes in the emulsions can vary widely, e.g., from 5-100 milligrams per liter of fiowable emulsion. The concentration of the dyes will vary somewhat according to the type of emulsion and according to the effect desired.

With most of our dyes, from 15 to 30 milligrams of dye per liter of emulsion (containing about 40 grams of silver halide) suflice to produce the maximum sensitizing effect. With the finer grain emulsions, somewhat larger concentrations of dye may be needed to produce the maximum sensitizing effect.

The new dyes of our invention have been found to be particularly useful since they operate to increase the sensitivity of photographic emulsions containing color formers fast to diffusion to a higher extent than comparable sensitizing dyes without the 6-cyanoethoxy-substituted benzothiazole nucleus. The sensitizing bands of the new dyes of our invention are unusually sharp so that they render themselves advantageously for use in color emulsions.

The invention is further illustrated by the following examples although it is to be understood that the invention is not restricted thereto.

PREPARATION OF INTERMEDIATES Example I 6HYDROXY-Z-METHYLBENZOTHIAZOLE A mixture of 48 grams of sodium hydroxide, 48 grams of potassium hydroxide and 24 grams of sodium sulfide nonahydrate (Na S.9H O) was placed in a copper beaker and heated to a temperature of 250 C. To the fused alkali was added 40 grams of 2-amino-6-methoxybenzothiazole. The mixture was stirred and maintained at 250-260 C. for seven minutes. Eight hundred milliliters of water were added and the solution filtered.

To this alkaline solution of substantially pure Z-amino- S-hydroxy-thiophenol was added 400 milliliters of acetic anhydride. After stirring for 30 minutes, the oil which had formed was separated and the solution extracted with five 400 milliliter portions of benzene. The oil and the extracts were combined and the benzene distilled off. The residue was refluxed with 400 milliliters of acetic anhydride for one hour and distilled. Twenty-four grams of solid was obtained which was substantially pure Z-methyl- 6-acetoxybenzothiazole; M.P. 182 C.

The 24 grams of freshly vacuum distilled 6-acetoxy-2- methylbenzothiazole were dissolved in 23.5 milliliters of methanol and 100 milliliters of water. The solution was heated on a steam bath for a total of 7 hours with stirring. During this time, an aqueous sodium hydroxide solution (6 normal) was added slowly in such a manner that the solution was kept slightly alkaline to litmus paper at all times. The solution was filtered while hot and the filtrate acidified with glacial acetic acid. The solution was allowed to cool overnight. The product which had precipitated in quantitative yield was filtered oif. For further purification, the compound was first recrystallized from methanol, then from ethanol, filtered off and washed with dry ether. The product was dried overnight at 50 C. The melting point of the analytically pure product was 163-164" C. sharp.

Example 11 2,5-DIMETHYL-G-HYDROXYBENZOTHIAZOLE C-GHa Into a 4-liter stainless steel beaker was charged 235 grams of sodium hydroxide pellets, 236 grams of potas sium hydroxide pellets and 80 grams of sodium sulfide (Na S.9H O). The mixture was heated to 240250 C. with vigorous mechanical stirring. Over a period of about 25 minutes was then added 200 grams of 2-amino-6-methoxy-S-methylbenzothiazole in small portions. Heating at 250 C. was continued for another 15 minutes. While stirring was continued, water was added to the black fusion mixture until the beaker was filled to within 5 cm. from the top. Stirring was continued for another 30 minutes. When the mixture had cooled down to about 55 C., it was filtered through a 21 cm. Buchner funnel, using about 100 milliliters of diatomaceous earth (Filter-Cel) as a filtering aid. The precipitate was washed once with hot water; the filtrate and the wash water were combined and allowed to cool. About 950 milliliters of acetic anhydride were added until the aqueous extract was slightly acidic. The mixture was stirred for one hour at 20 C. The precipitate which formed was filtered ofl, dried and then refluxed with 400 milliliters of acetic anhydride for one hour. The acetic anhydride was distilled off and the azole ring closure made by heating the diacetate for about 15 minutes. The resultant 2,S-dimethyl-6-acetoxybenzothiazole was then distilled under reduced pressure yielding about 80 grams of pure product.

The distillate was then dispersed in a solution consisting of 1 liter of water and 500 milliliters of methanol; aqueous sodium hydroxide (6 N) was added gradually, with continued stirring, to keep the stirred solution alkaline for six hours. During this time, the solution was kept at 75-80 C. and finally cooled to 5 C. The product was filtered and washed free of sodium hydroxide with Water. The 44.7 grams of crude material was recrystallized from methanol; 37.5 grams of a pure product melting at 203- 204 C. was obtained.

Example III 2-METIIYL-6-fi-CYANOETHOXYBENZOTHIAZOLE Eight grams (0.05 mole) of 2-methyl-6-hydroxybenzothiazole and 13.3 grams (0.25 mole) of freshly distilled acrylonitrile and 1 milliliter of benzyltrirnethylamomnium hydroxide (Triton B) were heated to reflux on a steam bath for 20 hours. To the hot solution was then added 150 milliliters of benzene and 2 grams of 6 (bone) charcoal. The black slurry was heated to reflux temperature for 10 minutes and then filtered through a Buchner funnel. The charcoal on the filter was extracted with hot benzene and the combined filtrates placed into a separatory funnel. The basic catalyst was removedby washing. The benzene solution was washed with distilled water until the wash water was neutral to alkacid paper. The benzene layer was then washed twice with 60 milliliter of a 2.5 percent aqueous sodium hydroxide solution in order to remove any unreacted 6-hydroxy-2-methylbenzothiazole. The benzene solution was subsequently washed with water until the wash water was neutral and then dried with anhydrous sodium sulfate overnight. Removal of the benzene and any acrylonitrile by distillation under aspirator vacuum yielded 7.60 grams of crude product. This material was crystallized from benzene. Yield: 6.6 grams; melting point 122-123. A second recrystallization from benzene did not raise the melting point.

Analysis for CnHmONgSZ Calculated 60. 53 4. 62 Found- 60. 59 4. 62

Example IV 2,5-DIMETHYL-6-(fl-CYANOETHOXY)BENZOTHIAZOLE s NCCH2CH2O C-CH3 Example III is repeated except that the 8 grams of 6- hydroxy-Z-methylbenzothiazole are replaced by 8.2 grams of 6-hydroxy-2,S-dimethylbenzothiazole.

Example V 6- (B-CYANOETHOXY) -2-METHYLBENZOTHIAZOLE ETHIODIDE Example VI 3- (fl-CARBOXYETHYL) -6- (B-CYANOETHOX Y) -2,5-DI- METHYLBENZOTHIAZOLIUM IODIDE NC-CHr-CHr-O CH /0 om C \I (3H2 ooon This product is obtained by heating 0.6 grams of 2,5- dirnethyl-6-(fl-cyanoethyl)benzothiazole and 5 grams of ,B-iodopropionic acid in a sealed bomb for 24 hours at 102 C. The resultant product is purified by trituration with ether, ethanol, acetone and again with ether.

7 Example VII 1',3-DIETHYL-6-METHOXY-6- (B-CYANOETHOXY) THIAPSEUDOCYANIN E IODIDE NO-CH CHz-O- oon NG-OH CH -O p a o-cn= One hundred eighty-seven milligrams (0.5 millimole) 8 Example IX 6'-(fi-CYANOETHOXY) -3,3,9-TRIE'IHYL-5-l\l'ETHOXY- SELENATHIACARBOCYANINEIODIDE O CH:

of 6-(fiy y) -l-methylbenzothiazole ethiodide ditions described in Example VIII. The dye was sepaand 190 milligrams mlllimele) 0f Y Pto-6- rated by centrifuging and the solvent decanted. The dye metlloxyqulnollne ethlodlde were dlSPeI'Sed in 7 milliliters was then purified by successive trituration with acetone, of methanol. Seven drops of triethylamine were added tha fl and ether, After drying, 250 mg. of dye was an h mixture heated to reflux for 5 m n Th obtained exhibiting a melting point range of 277-279. mixture was then cooled to room temperature and P This compound sensitized a photographic gelatino silver rated into 2 phases by centrifuging. The orange colored bromoiodide emulsion to about 660 millimicrons with a mother liquor was discarded and the y Purified y maximum sensitivity of about 625 millimicrons. cessive extraction with benzene, acetone and ether. After Exam 18 X drying, 155 milligrams of dye was obtained exhibiting a p melting point range of 303-305 This compound sensi- 3ETHYL'3"(H'CARBOXYETHYLl'5"METHYIG"(B tized a photographic gelatino silver bromoiodide emulsion CYANOETHOXY)'THIACARBOCYANINE IODIDE to about 520-580 millimicrons with a maximum sensi- S 0 tivity at about 540-560 millimicrons. NC-CHHCHTO CCH=GHOH=O Example VIII OH 4',5'-BENZO-6-(B-CYANOETHOXY)-3,9-DIETHYL-3'- A:

METHLYTHIACARBOCYANINE H2 2115 o H Twenty-five drops of triethylamine were added to a H n solution of 187 milligrams of 3-(,8-carboxyethy1)-6-(B- N cyanoethoxy) -2,S-dimethylbenzothiazolium iodide and 216 1 5 milligrams of Z-(IS-acetanilidovinyl) 3 ethylbenzothia- 2m zolium iodide in 20 milliliters of ethanol. The product 1- which separated on cooling was washed with ethanol,

acetone and ether. This application is a continuation-in-part of our co- One hundred eighty-seven milligrams (0.5 milllmole) pending application, Serial Number 724 274 filed on e-(fi-eyanoethoxy)jz-methylbenzothialole and 2785 March 27, 1958, now United States Patent 2,928,839. mllllgrame mllllmole) 0f -(I l/ -B' Various modifications of this invention will occur to methylmefeaptelflflyl)'benZetllieZele etllledlde were persons skilled in the art. Thus, our intermediates can persed in 7 milliliters of methanol to which seven drops be used not only f the preparation f monoand l tfletllylamlne e e added- The mixture was methine dyes of the types illustrated by the examples, but heated to reflux for 5 mlmltes on a steam bath- The lend themselves also to the preparation of merocyanine Slurry was cooled to q temperature, and Separated and styryl dyes. We, therefore, do not intend to be limlnte two Plleses y eenll'lfuglng- The liquid Porllen was ited to the patent granted except as necessitated by the discarded while the solid was purified by successive tritd d 1 m uration With isopropanol, acetone, methanol, benzene W l i and ether. After drying, 315 mg. of dye was obtained 1. A sensitizing dye selected from the group consisting which exhibited a melting point range of 238240. of the compounds of the following formulae:

S no-onioni-o o= oH-oH)e-i=o-(on=oH), ,-o on-oH)m-EN 1'1.

I t Y and i S No-o11iorn-o R1 a C=CH-(GH=CH)e-1 H- )n1= =l )Fi N R l These compounds sensitized photographic gelatino silver bromoiodide emulsions to about 665 millimicrons with the maximum sensitivity at about 625 millimicrons.

wherein m, n and p represent positive integers ranging from 1 to 2; R is a member selected from the class consisting of hydrogen and methyl; R is a member selected from the class consisting of methyl, ethyl, propyl, B-hydroxyethyl, -hydroxypropyl, allyl, carboxymethyl, carboxyethyl, benzyl and phenethyl; R and R represent members selected from the group consisting of hydrogen and lower alkyl groups; R being only hydrogen when n and p equal 1; R is a member selected from the group consisting of methyl, ethyl, propyl, butyl, amyl, hydroxymethyl, hydroxyethyl, hydroxypropyl, carboxymethyl, carboxyethyl, carboxypropyl, benzyl and phenethyl; Y represents an anion of the type used in cyanine dyes and Z represents the atoms necessary to complete a nitrogenous heterocyclic nucleus selected from the class consisting of a pyridine nucleus, a quinoline nucleus, a thiazoline nucleus, at benzoxazole nucleus, a benzothiazole nucleus, a benzoselenazole nucleus, a naphthoxazole nucleus, at naphthothiazole nucleus and a naphthoselenazole nucleus.

2. A sensitizing dye having the following formula:

S OCH:

C-CH

N C-CHzCHz-O- 4. A sensitizing dye having the following formula:

- zHg 5. A sensitizing dye having the following formula:

NCCH:CH2O 5 \C-CH=OHCH=C/ I N OH: 47211; $113 10 00 OH I- References Cited in the file of this patent UNITED STATES PATENTS 2,107,379 Koslowsky Feb. 8, 1938 2,126,078 Zeh et al. Aug. 9, 1938 2,345,094 Brooker et a1 Mar. 28, 1944 2,542,401 Doyle et al. Feb. 20, 1951 2,715,623 Fry et al. Aug. 16, 1955 2,918,369 Doorenbos Dec. 22, 1959 2,928,839 Roth et al Mar. 15, 1960 FOREIGN PATENTS 640,127 Great Britain July 12, 1950 OOHa 

1. A SENSITIZING DYE SELECTED FROM THE GROUP CONSISTING OF THE COMPOUNDS OF THE FOLLOWING FORMULAE:
 3. A SENSITIZING DYE HAVING THE FOLLOWING FORMULA: 